A fundamental study for long-distance noncontact shallow underground exploration technology by acoustic irradiation-induced vibration

Abstract

A fundamental study was conducted to investigate the possibility of shallow underground exploration from a long distance by acoustic irradiation-induced vibration. To detect buried objects in shallow underground, our method is proposed to excite the ground surface directly from above with sound waves and measure the vibration velocity distribution with a laser Doppler vibrometer. From the experimental results, it was found that the detection frequency is inversely proportional to the size of the buried object, but does not change much even if the buried depth is changed. It was also clarified that the buried object can be detected even if the grazing angle of the laser is about 20 degrees, and that it can be explored even at a distance of about 20 m. From these experiment results, it became clear that there is a possibility of shallow underground exploration using an unmanned aerial vehicle equipped with a small sound source.

Feasibility of nondestructive testing using transient vibrations excited by acoustic radiation force

“…Vibrations can be also excited on an object by ultrasonic irradiation from a fluid such as air or water. [3][4][5][6][7] By measuring the vibration velocity of the object's surface, e.g. with a laser Doppler vibrometer, internal defects can be detected without contact with a tested object.…”

Pulse compression of guided wave by airborne ultrasound excitation for improving defect detection accuracy in concrete

“…The methods use laser ultrasound, 12,13) electromagnetic ultrasound, 14,15) and air-coupled ultrasound. [16][17][18][19][20][21][22][23][24][25][26] Among them, the method using laser ultrasound is the most practical for long-distance irradiation, and in recent years, a technique has been developed for imaging defects in structures by using a scanning laser source. [27][28][29] In this method, a relatively lowfrequency pulse laser is irradiated from a distance to generate sound waves on the target.…”

Non-contact bolt axial force measurement based on the deformation of bolt head using quartz crystal resonator and coils

“…For underground and concrete structures, several methods based on the combination of sound waves and lasers have been reported. [1][2][3][4][5][6][7][8] On the other hand, as a repeatedly reported sensing device based on the frequency shift, the quartz crystal resonator is applied to microbalances 9) and force sensors. 10) It is based on the resonance frequency reduction upon the loading of a substance adsorbed on the surface of the resonator or a force applied to the resonator.…”